https://e621.net/posts/2721717?q=zero-sum
https://static1.e621.net/data/37/40/374094ef487c9e51647aae97b14d6dba.webm
FULL-https://static1.e621.net/data/39/6b/396b4c41c7bed09cedf9a136ce5caac3.webm
https://static1.e621.net/data/c9/50/c95083e2dd8aec3823ba4b77e77195e0.webm
https://static1.e621.net/data/34/a3/34a36af62cc9b00ba3e22c80207fa8d6.webm
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https://static1.e621.net/data/99/a0/99a0940397837d4c22d2372ff3fa7de7.webm